US11194278B2 - Image forming apparatus capable of forming image on both first side and second side of sheet - Google Patents

Image forming apparatus capable of forming image on both first side and second side of sheet Download PDF

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Publication number
US11194278B2
US11194278B2 US17/081,360 US202017081360A US11194278B2 US 11194278 B2 US11194278 B2 US 11194278B2 US 202017081360 A US202017081360 A US 202017081360A US 11194278 B2 US11194278 B2 US 11194278B2
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sheet
image
toner image
feeding
image forming
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US20210132534A1 (en
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Noriaki Matsui
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Canon Inc
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Canon Inc
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    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
    • G03G15/00—Apparatus for electrographic processes using a charge pattern
    • G03G15/22—Apparatus for electrographic processes using a charge pattern involving the combination of more than one step according to groups G03G13/02 - G03G13/20
    • G03G15/23—Apparatus for electrographic processes using a charge pattern involving the combination of more than one step according to groups G03G13/02 - G03G13/20 specially adapted for copying both sides of an original or for copying on both sides of a recording or image-receiving material
    • G03G15/231—Arrangements for copying on both sides of a recording or image-receiving material
    • G03G15/232—Arrangements for copying on both sides of a recording or image-receiving material using a single reusable electrographic recording member
    • G03G15/234—Arrangements for copying on both sides of a recording or image-receiving material using a single reusable electrographic recording member by inverting and refeeding the image receiving material with an image on one face to the recording member to transfer a second image on its second face, e.g. by using a duplex tray; Details of duplex trays or inverters
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
    • G03G15/00—Apparatus for electrographic processes using a charge pattern
    • G03G15/14—Apparatus for electrographic processes using a charge pattern for transferring a pattern to a second base
    • G03G15/16—Apparatus for electrographic processes using a charge pattern for transferring a pattern to a second base of a toner pattern, e.g. a powder pattern, e.g. magnetic transfer
    • G03G15/1665—Apparatus for electrographic processes using a charge pattern for transferring a pattern to a second base of a toner pattern, e.g. a powder pattern, e.g. magnetic transfer by introducing the second base in the nip formed by the recording member and at least one transfer member, e.g. in combination with bias or heat
    • G03G15/167—Apparatus for electrographic processes using a charge pattern for transferring a pattern to a second base of a toner pattern, e.g. a powder pattern, e.g. magnetic transfer by introducing the second base in the nip formed by the recording member and at least one transfer member, e.g. in combination with bias or heat at least one of the recording member or the transfer member being rotatable during the transfer
    • G03G15/168—Apparatus for electrographic processes using a charge pattern for transferring a pattern to a second base of a toner pattern, e.g. a powder pattern, e.g. magnetic transfer by introducing the second base in the nip formed by the recording member and at least one transfer member, e.g. in combination with bias or heat at least one of the recording member or the transfer member being rotatable during the transfer with means for conditioning the transfer element, e.g. cleaning
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
    • G03G15/00—Apparatus for electrographic processes using a charge pattern
    • G03G15/65—Apparatus which relate to the handling of copy material
    • G03G15/6555—Handling of sheet copy material taking place in a specific part of the copy material feeding path
    • G03G15/6558—Feeding path after the copy sheet preparation and up to the transfer point, e.g. registering; Deskewing; Correct timing of sheet feeding to the transfer point
    • G03G15/6561—Feeding path after the copy sheet preparation and up to the transfer point, e.g. registering; Deskewing; Correct timing of sheet feeding to the transfer point for sheet registration
    • G03G15/6564—Feeding path after the copy sheet preparation and up to the transfer point, e.g. registering; Deskewing; Correct timing of sheet feeding to the transfer point for sheet registration with correct timing of sheet feeding
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
    • G03G15/00—Apparatus for electrographic processes using a charge pattern
    • G03G15/65—Apparatus which relate to the handling of copy material
    • G03G15/6555—Handling of sheet copy material taking place in a specific part of the copy material feeding path
    • G03G15/6579—Refeeding path for composite copying
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
    • G03G21/00—Arrangements not provided for by groups G03G13/00 - G03G19/00, e.g. cleaning, elimination of residual charge
    • G03G21/14—Electronic sequencing control
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
    • G03G2215/00—Apparatus for electrophotographic processes
    • G03G2215/00362—Apparatus for electrophotographic processes relating to the copy medium handling
    • G03G2215/00535—Stable handling of copy medium
    • G03G2215/00548—Jam, error detection, e.g. double feeding
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
    • G03G2215/00—Apparatus for electrophotographic processes
    • G03G2215/00362—Apparatus for electrophotographic processes relating to the copy medium handling
    • G03G2215/00535—Stable handling of copy medium
    • G03G2215/00556—Control of copy medium feeding
    • G03G2215/00586—Control of copy medium feeding duplex mode
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
    • G03G2215/00—Apparatus for electrophotographic processes
    • G03G2215/00362—Apparatus for electrophotographic processes relating to the copy medium handling
    • G03G2215/00535—Stable handling of copy medium
    • G03G2215/00556—Control of copy medium feeding
    • G03G2215/00599—Timing, synchronisation

Definitions

  • the present invention relates to an image forming apparatus capable of forming an image on both a first side and a second side of a sheet.
  • Image forming apparatuses for forming a full color image transfer toner images each in a different color from photosensitive drums to an intermediate transfer belt (ITB) and then transfer the toner images from the ITB to a sheet.
  • ITB intermediate transfer belt
  • Such image forming apparatuses in order to improve productivity, start forming toner images on photosensitive drums before starting to feed a sheet.
  • a sheet jam occurs after toner image formation is started.
  • U.S. Pat. No. 8,059,976B1 it is proposed to retry feeding a sheet while handling a toner image as an invalid image.
  • a sheet that is fouled on the back side is defective as a product. Meanwhile, it is conceivable to stop conveying a sheet and then make the user remove the sheet before the sheet is fouled. However, this would be deficient in terms of usability. It would be possible to prevent the fouling on the back side if there were a mechanism to clean the secondary transfer unit in a short time, but such mechanism is expensive. If the toner image formation on the photosensitive drums is started only after confirming that a sheet has been conveyed without jamming, productivity would suffer. In view of this, the present invention aims to provide an image forming apparatus capable of maintaining productivity in double-sided image formation.
  • the present invention provides an image forming apparatus for forming an image on both a first side and a second side of a sheet.
  • the apparatus may comprise the following elements: an image forming unit configured to form a toner image on an image bearing member; a feeder configured to feed a sheet; a sheet detector configured to detect the sheet in a first conveyance path for conveying the sheet; a transfer unit configured to transfer the toner image formed on the image bearing member onto the sheet; a controller configured to control a timing for forming the toner image on the image bearing member and a timing for feeding the sheet and to control a conveyance of the sheet so that a timing that a toner image conveyed by the image bearing member arrives at the transfer unit and a timing that the sheet arrives at the transfer unit coincide; a fixing unit configured to fix onto the sheet the toner image transferred onto the sheet from the transfer unit; and a re-feeder configured to re-feed a sheet to the transfer unit in order to transfer a toner image onto a second side of the sheet onto whose first
  • FIG. 1 is a diagram for describing an image forming apparatus.
  • FIG. 2 is a diagram for describing a control system.
  • FIGS. 3A to 3D are diagrams for describing image formation intervals.
  • FIG. 4 is a diagram for describing conveyance positions of sheets.
  • FIG. 5 is a diagram for describing conveyance positions of sheets.
  • FIG. 6 is a diagram for describing conveyance positions of sheets.
  • FIG. 7 is a diagram for describing conveyance positions of sheets.
  • FIG. 8 is a diagram for describing conveyance positions of sheets.
  • FIG. 9 is a diagram for describing control timings.
  • FIG. 10 is a diagram for describing control timings.
  • FIG. 11 is a diagram for describing control timings.
  • FIG. 12 is a diagram for describing control timings.
  • FIG. 13 is a diagram for describing control timings.
  • FIG. 14 is a flowchart for describing image formation control.
  • FIG. 15 is a diagram for describing functions of a CPU.
  • FIG. 2 illustrates a control system of the image forming apparatus 100 .
  • a control unit 200 has a CPU 201 , a ROM 202 , and a RAM 203 .
  • the CPU 201 controls image formation and conveyance of the sheets P in accordance with a control program stored in the ROM 202 .
  • the CPU 201 saves in the RAM 203 and manages a position of each sheet, a position of an image, and such in a conveyance path.
  • Sheet sensors 2 a and 2 b , a flapper 4 a , and motors M 1 to M 7 are connected to the CPU 201 via an I/O 210 . Although other sheet sensors and motors are also connected to the CPU 201 , their relation to the present invention is small, and thus, are not illustrated.
  • the CPU 201 When a print instruction is inputted to the CPU 201 from a UI 230 , the CPU 201 starts control of an image forming unit 250 .
  • the CPU 201 controls generation of a charging voltage and a developing voltage for a processing unit 120 via the image forming unit 250 and generation of a transfer voltage and a cleaning voltage for a secondary transfer unit 140 .
  • the CPU 201 controls rotation of a transfer belt 130 and driving of an exposure device 110 via the image forming unit 250 .
  • the CPU 201 controls a temperature of a fixing device 170 to a target temperature via the image forming unit 250 .
  • the CPU 201 drives the motor M 1 via the I/O 210 , and then causes the motor M 1 to rotate rollers 1 a and 1 b .
  • the sheets P contained in the feeding cassette 20 are fed one at a time to a conveyance path 3 a .
  • the conveyance path 3 a is a main conveyance path present from the feeding cassette 20 to the flapper 4 a .
  • the CPU 201 uses the sheet sensor 2 a in order to monitor whether or not feeding of the sheet P is successful.
  • the roller 1 a is sometimes called a pickup roller.
  • the rollers 1 b are sometimes called separation rollers.
  • the CPU 201 drives the motors M 2 and M 3 and thereby rotates rollers 1 c , 1 d , and 1 e .
  • the rollers 1 c , 1 d , and 1 e are conveyance rollers for conveying the sheets P from an upstream side to a downstream side.
  • the CPU 201 may control rotation of rollers 1 f via the motor M 4 in accordance with a timing when the leading edge of the sheet P reaches the sheet sensor 2 b .
  • a timing when a toner image conveyed by the transfer belt 130 arrives at the secondary transfer unit 140 and a timing when the sheet P arrives at the secondary transfer unit 140 is matched.
  • the rollers 1 f are sometimes called registration rollers. Note that in a case where the timing when the leading edge of the sheet P arrives at the sheet sensor 2 b is earlier than a set timing, the CPU 201 stops the sheet P when the sheet P abuts against the rollers 1 f .
  • a position of the leading edge of the sheet P here is denoted as SP 3 .
  • the CPU 201 after stopping the sheet P for a time such that the timing when the toner image arrives at the secondary transfer unit 140 and the timing when the sheet P arrives at the secondary transfer unit 140 coincide, activates the motor M 4 to thereby convey the sheet P to the rollers 1 f.
  • the CPU 201 causes the exposure device 110 and the processing unit 120 to start image formation so to be on time for the timing when the sheet P arrives at the secondary transfer unit 140 .
  • the processing unit 120 has photosensitive drums, developing devices, charging rollers, drum cleaners, and such.
  • the image forming unit 250 uniformly charges a surface of the photosensitive drum and then causes the exposure device 110 to irradiate a laser beam onto the photosensitive drum. By this, an electrostatic latent image is formed on the photosensitive drum.
  • the image forming unit 250 develops the electrostatic latent image with the developing device to thereby form a toner image.
  • a primary transfer unit 121 transfers the toner image from the photosensitive drum to the transfer belt 130 .
  • the image forming unit 250 rotates the transfer belt 130 and then conveys the toner image to the secondary transfer unit 140 .
  • a belt cleaner 131 cleans and collects toner remaining on the transfer belt 130 that was not transferred onto the sheet P by the secondary transfer unit 140 .
  • the image forming unit 250 by applying the cleaning voltage to the secondary transfer unit 140 , retransfers the toner adhered to the secondary transfer unit 140 to the transfer belt 130 and then collects the toner in the belt cleaner 131 .
  • the polarity of the cleaning voltage is the opposite of the polarity of the transfer voltage for transferring the toner image onto the sheet P.
  • the sheet P is conveyed to the fixing device 170 .
  • the fixing device 170 fixes the toner image onto the sheet P by adding heat and pressure in relation to the sheet P and the toner image.
  • the conveyance path 3 a branches out to conveyance paths 3 c and 3 b on the downstream side of rollers 1 g .
  • the CPU 201 guides the sheet P to the conveyance path 3 c or 3 b by controlling the flapper 4 a .
  • the sheet P onto whose first side an image is formed is guided to the conveyance path 3 b .
  • the sheet P onto whose second side an image was formed in the double-sided printing job and the sheet P onto whose first side an image was formed in a single-sided printing job are guided to the conveyance path 3 c .
  • the CPU 201 drives the motor M 5 in order to rotate rollers 1 h and discharge the sheet P from a discharge port 196 onto a sheet discharge tray 197 .
  • Conveyance paths 3 b , 3 d , and 3 e are also called double-sided conveyance paths as they convey the sheet P to be double-sided printed.
  • the conveyance path 3 b branches out to conveyance paths 3 d and 3 e on the upstream side of rollers 1 i .
  • Rollers 1 i and 1 j pull the sheet P into the conveyance path 3 d from the conveyance path 3 b with the motor M 6 and then switch from a normal rotation to a reverse rotation. Note that the sheet P may temporarily wait in the conveyance path 3 d .
  • the sheet P is guided to the conveyance path 3 e by a flapper 4 b .
  • the flapper 4 b is a so-called mechanical flapper.
  • the sheet P is conveyed by rollers 1 k , 1 l , and 1 m , and a refeed timing of the sheet P is adjusted by rollers 1 n .
  • the rollers 1 k to 1 n are driven by the motor M 7 .
  • a position of the rollers 1 n may be called a refeed position SP 2 .
  • the sheet P conveyed by the rollers 1 n is fed to the conveyance path 3 a again.
  • the sheet P is conveyed by the rollers 1 d , 1 e , and 1 f and is fed to the secondary transfer unit 140 , and then an image is formed on the second side.
  • a formation order of toner images in a case where an image is formed on both sides of n sheets of the sheets P and then the side on which the image was formed first is discharged face-down on the sheet discharge tray 197 , is as follows. Numbers in a parentheses indicate the formation order (a page number) of the toner images.
  • Numbers given to the sheets P and the toner images indicate the number of the sheet.
  • An “f” given to toner images indicates a front side (the first side).
  • a “b” given to toner images indicates a back side (the second side).
  • the toner image for the front side and the toner image for the back side are formed alternatingly. In order to achieve high productivity, such alternating printing is effective.
  • a distance from the trailing edge of a preceding toner image to the leading edge of a next toner image on the transfer belt 130 is sometimes called an image formation interval.
  • a distance (a conveyance interval) from the trailing edge of a preceding sheet to the leading edge of the next sheet on the secondary transfer unit 140 is sometimes called a sheet interval.
  • high productivity is achieved by maintaining a constant image formation interval and sheet interval.
  • FIG. 3A illustrates an ideal case 0 where the image formation interval is a constant time T 0 .
  • the CPU 201 outputs a TOP signal to the image forming unit 250 when the processing unit 120 becomes capable of image formation. By this, the image forming unit 250 outputs the image signal to the exposure device 110 , and then toner image formation starts.
  • the TOP signal is a signal for starting toner image formation.
  • output timings of TOP signals for a second and subsequent toner images are sometimes adjusted by the CPU 201 in accordance with whether or not the sheet P feed delay is occurring.
  • FIG. 4 illustrates positions of toner images and positions of the sheets P in the case 0.
  • the sheet P 1 onto whose first side an image is formed is present on the conveyance path 3 e .
  • a toner image I 2 f is being transferred onto a first side of a sheet P 2 .
  • a toner image I 1 b is being conveyed following the toner image I 2 f .
  • formation of a toner image I 3 b is started.
  • feeding cassette 20 feeding of a sheet P 3 is started.
  • FIG. 5 illustrates positions of toner images and positions of the sheets P at a time later than the time of the case illustrated in FIG. 4 .
  • the toner image I 1 b is being transferred onto a second side of the sheet P 1 .
  • the sheet P 2 on whose first side a toner image is formed is being conveyed through the conveyance paths 3 b and 3 d .
  • a sheet P 3 is being successfully fed.
  • FIG. 3B illustrates a case I where the TOP signal of the toner image I 1 b was caused to be delayed due to a feed delay of the sheet P 3 occurring.
  • FIG. 6 illustrates positions of toner images and positions of the sheets P in the case I.
  • the toner image I 1 b is about to be transferred in relation to a second side of the sheet P 1 .
  • the toner image I 3 f is present on the transfer belt 130 .
  • a toner image I 2 b has not been formed yet.
  • the CPU 201 may delay the formation of the toner image I 2 b .
  • an image formation interval between the preceding toner image I 3 f and the next toner image I 2 b is T 1 (T 1 >T 0 ).
  • the sheet P 1 whose image formation of the second side is complete is conveyed toward the discharge port 196 .
  • the leading edge of the sheet P 3 is detected by the sheet sensor 2 a before a predetermined time Td 2 has elapsed from when the CPU 201 started the driving of the motor M 1 .
  • the CPU 201 determines that feeding of the sheet P 3 is successful. In a case where the feeding of the sheet P 3 is successful within the predetermined time Td 2 , by reducing the stop time of the sheet P 3 at the rollers 1 f , the arrival timing of the toner image I 3 f and the arrival timing of the sheet P 3 coincide.
  • the CPU 201 causes the processing unit 120 to start image formation of the toner image I 2 b at a timing that the sheet sensor 2 a is turned on. In other words, the CPU 201 waits until the sheet P 3 is detected by the sheet sensor 2 a and then starts the image formation of the toner image I 2 b . Thus, an image formation interval between the toner image I 3 f and the toner image I 2 b becomes T 1 which is longer than an initial value T 0 . In conjunction with this, the CPU 201 causes the sheet P 2 to wait at a standby position SP 2 and then re-feeds it.
  • the CPU 201 in a case ( FIG. 3C ) where the image formation interval between the toner image I 3 f and the toner image I 2 b exceeds T 2 , starts the image formation of the toner image I 2 b by the processing unit 120 . As illustrated in FIG. 8 , the CPU 201 cleans the toner image I 3 f adhered to the secondary transfer unit 140 simultaneously to the image formation of the toner image I 2 b .
  • the CPU 201 causes the toner image I 3 f to adhere (retransfers) to the transfer belt 130 by applying a cleaning voltage to the secondary transfer unit 140 from a transfer power supply 1530 ( FIG. 15 ).
  • the toner image I 3 f is conveyed to the belt cleaner 131 by the transfer belt 130 and then the belt cleaner 131 collects the toner image I 3 f .
  • the CPU 201 switches from the cleaning voltage to the transfer voltage at a timing such that by the time the toner image I 2 b that is the next page arrives at the secondary transfer unit 140 , the switch from the cleaning voltage to the transfer voltage is complete.
  • the time it takes for this switch is called a transition time, and the CPU 201 executes the switch at a timing that is earlier by the transition time to the timing that the toner image I 2 b arrives at the secondary transfer unit 140 .
  • the CPU 201 is able to resume image formation in a relatively short time by aiming to start the image formation of the toner image I 2 b at a timing when a time T 2 has elapsed. Also, the CPU 201 executes re-feeding of the sheet P 2 by the rollers In so that the arrival timing of the sheet P 2 and the arrival timing of the toner image I 2 b coincide.
  • the CPU 201 performs, as illustrated in FIG. 3D , the image formation of the toner image I 3 f again after the toner image I 2 b . This is called an image formation retry. Note that because the toner image I 3 f is already cleaned, the reformed toner image I 3 f may be called a toner image I 4 f in data processing.
  • FIG. 9 is a diagram describing a relationship between positions of sheets, feed timings, and TOP signals in the case 0 ( FIGS. 4 and 5 ).
  • the CPU 201 outputs a TOP signal in order to start the formation of the toner image I 3 f .
  • the CPU 201 outputs an M 1 on signal in order to activate the motor M 1 and then starts the feeding of the sheet P 3 by the motor M 1 .
  • An interval between the time t 10 and the time t 11 is normally a constant.
  • the CPU 201 detects that the sheet sensor 2 a has turned on.
  • Td 1 is a time for correcting a variation in a time (a travel time) that the sheet P 3 , which started being fed at the time t 11 , took to reach the position SP 1 .
  • Td 1 is adjusted to be short if the travel time is long, and Td 1 is adjusted to be long if the travel time is short.
  • a travel timing of the sheet P to a position SP 3 is controlled to be a constant.
  • the sheet P 3 arrives later than the toner image I 3 f in relation to the secondary transfer unit 140 .
  • the toner image I 1 b is approaching the secondary transfer unit 140 .
  • the transfer belt 130 further on an upstream side of the toner image I 1 b , the toner image I 3 f has already been transferred. Even further on the upstream side, a transfer of the toner image I 2 b onto the transfer belt 130 has been started.
  • the sheet sensor 2 a detects the sheet P 3 at the time t 12 and then the CPU 201 outputs the TOP signal for the toner image I 2 b at a time t 13 .
  • An interval between a preceding TOP signal and a next TOP signal is Tcom.
  • Tcom is 750 ms.
  • productivity is predefined depending on a size of sheets or a type of sheets (weight and such).
  • the CPU 201 generates an M 4 on signal at times t 15 and t 16 , which are after a time Timg has elapsed from the times t 10 and t 13 , respectively, when the TOP signal was outputted.
  • the motor M 4 is activated, the rollers 1 f rotate, and then the conveyance of sheets P 3 and P 2 stopped at the position SP 3 is resumed.
  • the time Timg is a predetermined time based on a difference between a time that a toner image formed by the TOP signal as a trigger reaches the secondary transfer unit 140 and a time that the sheet P starts moving based on the M 4 on signal and then reaches the secondary transfer unit 140 .
  • a refeed timing of the sheet P 2 is a time t 14 when a predetermined time Tfeed has elapsed from the time t 10 .
  • the re-feed is realized by the rollers 1 k to In and the rollers 1 d and 1 e .
  • the motor M 7 is driven by an M 7 on signal and then the rollers 1 k to In rotate.
  • the motor M 3 is driven by an M 3 on signal and then the rollers 1 d and 1 e rotate.
  • An output timing of the M 3 on signal in re-feed may be the same as an output timing of the M 7 on signal.
  • the re-fed sheet P 2 is conveyed to the rollers 1 f and then stops at the position SP 3 .
  • FIG. 10 illustrates a case (a comparative example) where a feeding of the sheet P 3 is delayed by Td 1 .
  • This comparative example is a case where the CPU 201 does not wait for the sheet sensor 2 a to detect the sheet P 3 and then outputs a TOP signal at the time t 13 .
  • a timing that the sheet P 3 arrives at the sheet sensor 2 a is a time t 12 - 1 which is delayed from the time t 12 by the time Td 1 .
  • the CPU 201 adjusts the time Td 1 , over which the sheet P 3 is stopped at the position SP 1 , to 0. Accordingly, the sheet P 3 is conveyed without stopping at the position SP 1 .
  • the CPU 201 must determine that a jam has occurred regarding the sheet P 3 . As described above, if the CPU 201 does not wait for the sheet sensor 2 a to detect the sheet P 3 and then outputs a TOP signal at the time t 13 , the sheet P 2 will be fouled.
  • the CPU 201 waits until the sheet sensor 2 a detects the sheet P 3 and then outputs the TOP signal. By this, the sheet P 2 is less likely to be fouled.
  • the CPU 201 delays the output of the TOP signal for the toner image I 2 b .
  • the CPU 201 generates a TOP signal in a case where the sheet sensor 2 a is already turned on when the time Tcom has elapsed from the time t 10 .
  • the conveyance and image formation of sheets after passing through the position SP 1 is as described in FIG. 10 .
  • a case illustrated in FIG. 12 is a case where feeding of the sheet P 3 is further delayed than the case illustrated in FIG. 11 .
  • the sheet sensor 2 a is unable to detect the sheet P 3 even at a time t 17 when the time Td 2 has elapsed from the time tn.
  • the CPU 201 stops the motor M 1 .
  • the CPU 201 outputs the TOP signal for the toner image I 2 b at a time t 13 - 2 when a time Td 2 +Td 3 has elapsed from the time tn.
  • the time t 13 - 2 is a time when a time Tcom+ ⁇ has elapsed from the time t 10 .
  • the time t 13 - 2 when the TOP signal for the toner image I 2 b is outputted is delayed by a time 3 - a in relation to the time t 13 - 1 .
  • the toner image I 3 f that was formed for the sheet P 3 which is not detected by the sheet sensor 2 a , can be cleaned by the cleaning voltage and the belt cleaner 131 .
  • the toner image I 3 f can be removed from the secondary transfer unit 140 , and thus, even if the toner image I 2 b is transferred onto the second side of the sheet P 2 , the first side of the sheet P 2 will be less likely to be fouled by the toner image I 3 f .
  • the CPU 201 causes the sheet P 2 that was re-fed from the double-sided conveyance path to wait at the position SP 3 .
  • the CPU 201 executes an image formation retry of the toner image I 3 f .
  • an image that is the same as the toner image I 3 f is formed as the toner image I 4 f .
  • a sheet P 4 in FIG. 13 is described as a sheet fed next from the feeding cassette 20 after P 2 , the sheet P 3 and the sheet P 4 are essentially the same sheet.
  • the image formation interval between the toner image I 2 b and the toner image I 4 f is T 3 .
  • the CPU 201 starts the driving of the motor M 1 at a time t 20 when a time Tfeed_C 1 elapses from the time t 13 . Because the sheet sensor 2 a detected the sheet P 4 at a time t 21 , the CPU 201 outputs the TOP signal for the toner image I 4 f . In the image formation retry, it is assumed that the CPU 201 does not generate a TOP signal until a feeding of the sheet P 4 is successful. Furthermore, the CPU 201 may improve the probability of the feeding being successful by executing the feeding under a condition that is advantageous for the feeding of the sheet P 4 .
  • An advantageous condition for example, is to cause the acceleration of the motor M 1 to be lower than a default setting value. Another advantageous condition is to cause the feeding speed (the rotation speed of the motor MD of the sheet P 4 to be lower than a default setting value. Another advantageous condition is to provide vibrations to the sheet P 4 by repeatedly driving and stopping the motor M 1 . At least one of a plurality of these advantageous conditions is executed.
  • the CPU 201 continuously conveys the sheet P 4 without stopping it at SP 1 . This is to improve productivity.
  • FIG. 14 is a diagram for describing image formation control of a toner image.
  • image formation control in relation to a sheet fed from the feeding cassette 20 mainly is described primarily.
  • temperature control of the fixing device 170 switching control of the flapper 4 a , and conveyance control related to the conveyance paths 3 a to 3 e are executed, as previously described, simultaneously with the image formation control.
  • the CPU 201 executes the following steps when the double-sided printing job is inputted from the UI 230 .
  • the CPU 201 by analyzing the double-sided printing job, creates and then holds in the RAM 203 monitoring information for each page.
  • the monitoring information may be created with a toner image as a page.
  • the monitoring information includes control information indicating that a toner image on a j-th page is formed on a first side (or a second side) of an i-th sheet P.
  • step S 1 the CPU 201 determines whether or not an output condition of a TOP signal is satisfied.
  • An output condition for a first sheet and an output condition for a second and subsequent sheets of a job are different.
  • the output condition of the first sheet is that the processing unit 120 is in a state in which image formation is possible. It is assumed that the CPU 201 monitors via the image forming unit 250 whether or not the processing unit 120 is capable of image formation.
  • a fundamental output condition regarding the second and subsequent sheets is that the time Tcom has elapsed from a time an immediately previous TOP signal was outputted.
  • the CPU 201 advances the processing to step S 2 when the output condition is satisfied.
  • step S 2 the CPU 201 determines whether or not the j-th page that is the image formation target is a second side of a sheet.
  • the CPU 201 holds the monitoring information for each page in the RAM 203 .
  • the CPU 201 determines whether the j-th page is a toner image of a second side or a toner image of a first side of a sheet by referring to the monitoring information regarding the j-th page.
  • the CPU 201 advances the processing to step S 3 if the j-th page is a second side.
  • step S 3 the CPU 201 determines whether or not a (j ⁇ 1)th page is a toner image of a first side.
  • the CPU 201 advances the processing to step S 4 if the (j ⁇ 1)th page is a toner image of a first side.
  • step S 4 the CPU 201 determines whether or not a sheet corresponding to the (j ⁇ 1)th page has been detected by the sheet sensor 2 a .
  • the sheet corresponding to the (j ⁇ 1)th page is a sheet onto which a toner image of the (j ⁇ 1)th page is scheduled to be transferred.
  • the CPU 201 advances the processing to step S 5 if the sheet has been detected by the sheet sensor 2 a.
  • step S 5 the CPU 201 generates and then outputs to the image forming unit 250 a TOP signal for a (j ⁇ 1)th page in order to start the image formation of a toner image.
  • the image forming unit 250 receives the TOP signal and then outputs an image signal to the exposure device 110 .
  • the exposure device 110 outputs a laser beam in accordance with the image signal.
  • the processing unit 120 starts the image formation of the toner image.
  • step S 6 the CPU 201 refers to the monitoring information in order to determine whether or not the job has ended. If the job is ended, the CPU 201 ends the image formation processing of the example. The CPU 201 advances the processing to step S 1 if the job is not ended.
  • step S 4 if it is determined that a sheet is not detected, the CPU 201 advances the processing to step S 10 .
  • step S 10 the CPU 201 determines whether or not the predetermined time Td 2 has elapsed from the time the feeding of the sheet was started. The CPU 201 advances the processing to step S 4 if the predetermined time Td 2 has not elapsed. The CPU 201 advances the processing to step S 11 if the predetermined time Td 2 has elapsed. As described above, steps S 4 and S 10 determine whether or not a sheet is detected within the predetermined time Td 2 .
  • step S 11 the CPU 201 stops the motor M 1 in order to stop the feeding of a sheet from the feeding cassette 20 .
  • the CPU 201 determines whether or not Td 2 +Td 3 has elapsed from the time the feeding was started. If Td 2 +Td 3 has not elapsed from a time when the feeding is started, the CPU 201 waits for Td 2 +Td 3 to elapse from a time when the feeding is started. By this, an image that was scheduled to be transferred onto a sheet that failed to be fed is cleaned.
  • the CPU 201 during Td 2 +Td 3 , applies the cleaning voltage from the transfer power supply 1530 onto the secondary transfer unit 140 and then cleans the toner image.
  • step S 13 the toner image that was scheduled to be transferred onto the sheet that was not detected within the predetermined time Td 2 is cleaned.
  • step S 13 the CPU 201 executes an image formation retry. As described using FIG. 13 , the CPU 201 activates the motor M 1 at a predetermined timing in order to start the feeding of a sheet. Furthermore, the CPU 201 generates and outputs a TOP signal to the image forming unit 250 . By this, a cleaned toner image is formed again.
  • step S 20 the CPU 201 generates and outputs a TOP signal in order to start the image formation of a toner image. Then, the CPU 201 advances the processing to step S 6 .
  • the image forming operation may be stopped, and the user may be made to perform jam processing.
  • the CPU 201 executes a control program in order to realize various functions.
  • One or all of these functions may be realized by a hardware circuit such as an ASIC or an FPGA.
  • An ASIC is an abbreviation for an application specific integrated circuit.
  • An FPGA is an abbreviation for a field programmable gate array.
  • An image formation control portion 1500 uses several timers in order to control an output timing (an image formation timing) of the TOP signal mainly.
  • a feeding control portion 1510 uses several timers in order to control the feeding and the conveyance of the sheet P mainly.
  • functions related to the feeding and the re-feeding of the sheet P mainly are described.
  • a Tcom timer 1501 included in the image formation control portion 1500 is a timer that times the predetermined time Tcom.
  • the Tcom timer 1501 is reset when a TOP signal is inputted.
  • a delay determination unit 1502 determines whether or not the predetermined time Tcom has elapsed. Also, the delay determination unit 1502 , when the predetermined time Tcom has elapsed, determines whether or not the sheet sensor 2 a has already detected a sheet. In a case where the sheet sensor 2 a has already detected a sheet when the predetermined time Tcom has elapsed, the delay determination unit 1502 outputs a TOP signal. If that is not the case, the delay determination unit 1502 does not output a TOP signal.
  • a Td 2 timer 1503 is a timer that starts timing a threshold time Td 2 when feeding from the feeding cassette 20 is started.
  • a jam determination unit 1504 determines whether or not the sheet sensor 2 a has detected a sheet before the Td 2 timer 1503 completes the timing of the threshold time Td 2 . If a sheet is detected within the threshold time Td 2 , the jam determination unit 1504 outputs a TOP signal. In a case (a Td 2 timeout) where a sheet is not detected within the threshold time Td 2 , the jam determination unit 1504 determines that a feed jam has occurred to the sheet and does not output a TOP signal.
  • a Td 3 timer 1505 is a timer in charge of an image formation retry.
  • the Td 3 timer 1505 starts timing a margin time Td 3 when a Td 2 timeout occurs.
  • the Td 3 timer 1505 when the timing of the margin time Td 3 is complete, outputs a TOP signal. By this, an image formation retry is executed.
  • a Tfeed timer 1511 included in the feeding control portion 1510 is a timer that times a predetermined time Tfeed when a TOP signal is inputted.
  • the Tfeed timer 1511 when the timing of the predetermined time Tfeed is complete, outputs the M 7 on signal and the M 3 on signal. By this, a sheet is re-fed from a re-feeding unit and then an image is formed on a second side of a sheet.
  • a Timg timer 1512 is a timer that starts timing a predetermined time Timg when the TOP signal is inputted.
  • the Timg timer 1512 when the timing of the predetermined time Timg is complete, outputs the M 4 on signal, drives the motor M 4 , and thereby rotates the rollers 1 f .
  • a timing that the sheet P arrives at the secondary transfer unit 140 and a timing that a toner image arrives at the secondary transfer unit 140 are synchronized.
  • a Tfeed_c 1 timer 1513 is a timer that times a predetermined time Tfeed_c 1 when the TOP signal for an image formation retry is inputted.
  • the Tfeed_c 1 timer 1513 completes timing the predetermined time Tfeed_c 1 , outputs the M 1 on signal, and then activates the motor M 1 .
  • Note that for the TOP signal to be inputted means to use the TOP signal as a trigger.
  • a cleaning control unit 1520 in a case where the sheet sensor 2 a does not detect a sheet even after a predetermine time has elapsed, causes the transfer power supply 1530 to output the cleaning voltage.
  • the transfer power supply 1530 may be, for example, a part of the image forming unit 250 .
  • the image forming apparatus 100 is an example of an image forming apparatus capable of forming an image on both a first side and a second side of a sheet.
  • the image forming apparatus 100 may be realized by any of a printer, a facsimile apparatus, a copying machine, or a multi-function peripheral.
  • the exposure device 110 , the processing unit 120 , and such function as an image forming unit for forming a toner image onto an image bearing member.
  • the transfer belt 130 and the photosensitive drum are examples of the image bearing member.
  • the motor M 1 and the roller 1 a function as a feeder for feeding a sheet.
  • the CPU 201 functions as a controller for controlling a timing for forming a toner image onto the image bearing member and a timing for feeding a sheet.
  • the sheet sensor 2 a functions as a sheet detector for detecting a sheet in a first conveyance path for conveying a sheet (e.g., the conveyance path 3 a ).
  • the secondary transfer unit 140 functions as a transfer unit for transferring a toner image formed on the image bearing member onto a sheet.
  • the transfer power supply 1530 for generating a cleaning voltage functions as a voltage supply unit for supplying the cleaning voltage to the transfer unit.
  • the rollers 1 f function as control rollers for controlling conveyance of a sheet so as that a timing that the sheet arrives at the transfer unit and a timing that a toner image conveyed by the image bearing member arrives at the transfer unit coincide.
  • the rollers 1 f function as controllers for controlling a timing for forming a toner image onto the image bearing member and a timing for feeding a sheet.
  • the fixing device 170 functions as a fixing unit for fixing onto a sheet a toner image transferred onto the sheet from the transfer unit.
  • the rollers In arranged in the conveyance path 3 e function as a re-feeder for re-feeding a sheet to the transfer unit in order to transfer a toner image onto a second side of the sheet onto whose first side a toner image has been fixed.
  • the CPU 201 outputs to the image forming unit a first start signal for causing the image forming unit to start forming a toner image to transfer onto a first side of an i-th sheet P 3 .
  • the TOP signal described above is an example of a start signal.
  • the CPU 201 causes the feeder to start feeding the i-th sheet P 3 . As illustrated in FIG.
  • the CPU 201 when a predetermined time (e.g., Tcom) has elapsed from when the first start signal was outputted, determines whether or not the i-th sheet has already been detected by the sheet detector. There are cases where, when the predetermined time has elapsed from when the first start signal was outputted, the i-th sheet has already been detected by the sheet detector. In such a case, the CPU 201 outputs to the image forming unit a second start signal for causing the image forming unit to start forming a toner image (e.g., I 2 b ) to be transferred onto a second side of an (i ⁇ 1)th sheet P 2 waiting at the re-feeder.
  • a predetermined time e.g., Tcom
  • the CPU 201 waits until the i-th sheet P 3 is detected by the sheet detector and then outputs to the image forming unit the second start signal. By this, productivity in the double-sided image formation is maintained.
  • the CPU 201 outputs the second start signal to the image forming unit.
  • the CPU 201 interrupts the feeding of the i-th sheet by the feeder.
  • the CPU 201 supplies the cleaning voltage to clean the toner image which was supposed to be transferred onto a first side of the i-th sheet adhered to the transfer unit and then outputs the second start signal to the image forming unit.
  • the CPU 201 after the feeding of the i-th sheet is interrupted and the feeding of the (i ⁇ 1)th sheet by the re-feeder is executed, causes the feeder to execute the re-feeding of the i-th sheet. By this, an opportunity for image formation in relation to the i-th sheet for which the feeding failed is granted again.
  • the motor M 1 functions as a motor for driving the feeder.
  • the CPU 201 may cause the acceleration of the motor adopted for the re-feeding of the i-th sheet to be lower than the acceleration of the motor adopted for the feeding of the i-th sheet.
  • the CPU 201 may cause the rotation speed of the motor adopted for the re-feeding of the i-th sheet to be lower than the rotation speed of the motor adopted for the feeding of the i-th sheet.
  • the CPU 201 may provide vibrations to a sheet by repeating rotation and stoppage of the motor and then re-feed the i-th sheet. By this, probability of the re-feeding of the i-th sheet being successful would improve.
  • the threshold time (e.g., Td 2 ) may be a time set in order to determine a sheet fed by the feeder as jammed.
  • a timing the second start signal is outputted may be a timing when a margin time (e.g., Td 3 ) has elapsed from a time when the threshold time elapsed.
  • the margin time may be, for example, a time for completing the supply of the cleaning voltage to the transfer unit by a voltage supply unit.
  • the transfer power supply 1530 functions as the voltage supply unit for supplying the cleaning voltage to the transfer unit so that the toner adheres again in relation to the image bearing member from the transfer unit.
  • the belt cleaner 131 functions as the collection unit for collecting the toner that adhered again onto the image bearing member.
  • Embodiment(s) of the present invention can also be realized by a computer of a system or apparatus that reads out and executes computer executable instructions (e.g., one or more programs) recorded on a storage medium (which may also be referred to more fully as a ‘non-transitory computer-readable storage medium’) to perform the functions of one or more of the above-described embodiment(s) and/or that includes one or more circuits (e.g., application specific integrated circuit (ASIC)) for performing the functions of one or more of the above-described embodiment(s), and by a method performed by the computer of the system or apparatus by, for example, reading out and executing the computer executable instructions from the storage medium to perform the functions of one or more of the above-described embodiment(s) and/or controlling the one or more circuits to perform the functions of one or more of the above-described embodiment(s).
  • computer executable instructions e.g., one or more programs
  • a storage medium which may also be referred to more fully as a
  • the computer may comprise one or more processors (e.g., central processing unit (CPU), micro processing unit (MPU)) and may include a network of separate computers or separate processors to read out and execute the computer executable instructions.
  • the computer executable instructions may be provided to the computer, for example, from a network or the storage medium.
  • the storage medium may include, for example, one or more of a hard disk, a random-access memory (RAM), a read only memory (ROM), a storage of distributed computing systems, an optical disk (such as a compact disc (CD), digital versatile disc (DVD), or Blu-ray Disc (BD)TM), a flash memory device, a memory card, and the like.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Control Or Security For Electrophotography (AREA)
  • Electrostatic Charge, Transfer And Separation In Electrography (AREA)
  • Paper Feeding For Electrophotography (AREA)
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Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20080025737A1 (en) 2006-07-25 2008-01-31 Canon Kabushiki Kaisha Image forming apparatus
US8229315B2 (en) * 2009-05-20 2012-07-24 Canon Kabushiki Kaisha Image forming apparatus and control method therefor
US20190212689A1 (en) 2018-01-10 2019-07-11 Canon Kabushiki Kaisha Image forming apparatus
US10527998B2 (en) 2016-06-29 2020-01-07 Canon Kabushiki Kaisha Image forming apparatus, jam processing method

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JPH08169632A (ja) * 1994-12-16 1996-07-02 Canon Inc 給紙装置
JP2001296785A (ja) * 2000-04-14 2001-10-26 Ricoh Co Ltd 作像タイミング制御方法および画像形成装置
US8019237B2 (en) * 2008-01-16 2011-09-13 Xerox Corporation Systems and methods for modifying feed timing for image receiving media in an image forming device
JP2013105029A (ja) * 2011-11-14 2013-05-30 Canon Inc 画像形成装置
JP2016090820A (ja) * 2014-11-05 2016-05-23 キヤノン株式会社 画像形成装置

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US20080025737A1 (en) 2006-07-25 2008-01-31 Canon Kabushiki Kaisha Image forming apparatus
JP2008052257A (ja) 2006-07-25 2008-03-06 Canon Inc 画像形成装置
US8059976B2 (en) * 2006-07-25 2011-11-15 Canon Kabushiki Kaisha Image forming apparatus with sheet feeding retry function
US8229315B2 (en) * 2009-05-20 2012-07-24 Canon Kabushiki Kaisha Image forming apparatus and control method therefor
US10527998B2 (en) 2016-06-29 2020-01-07 Canon Kabushiki Kaisha Image forming apparatus, jam processing method
US20190212689A1 (en) 2018-01-10 2019-07-11 Canon Kabushiki Kaisha Image forming apparatus

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